From: Martin Sperl <[email protected]> This avoid unnecessary mapping of null pages in sg_lists for masters that do not need a sg_list when rx_buf/tx_buff == NULL avoid.
Only spi-masters that require a mapped scatter-gather map need to set this, but they would not need to set SPI_MASTER_MUST_RX/TX. Signed-off-by: Martin Sperl <[email protected]> --- drivers/spi/spi.c | 38 +++++++++++++++++++------------------- include/linux/spi/spi.h | 2 ++ 2 files changed, 21 insertions(+), 19 deletions(-) Note that this is an optional patch to avoid the overhead for spi_masters that do not need the dummy-page functionality. diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 7e1a12c..9205928 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -570,25 +570,25 @@ static int __spi_map_msg(struct spi_master *master, struct spi_message *msg) if (!master->can_dma(master, msg->spi, xfer)) continue; - /* potentially add a flag to spi_master - * (SPI_MASTER_MUST_TX_SG) to avoid unnecessary mapping - */ - ret = spi_map_buf(master, tx_dev, &xfer->tx_sg, - (void *)xfer->tx_buf, xfer->len, - DMA_TO_DEVICE); - if (ret != 0) - return ret; - - /* potentially add a flag to spi_master - * (SPI_MASTER_MUST_RX_SG) to avoid unnecessary mapping - */ - ret = spi_map_buf(master, rx_dev, &xfer->rx_sg, - xfer->rx_buf, xfer->len, - DMA_FROM_DEVICE); - if (ret != 0) { - spi_unmap_buf(master, tx_dev, &xfer->tx_sg, - DMA_TO_DEVICE); - return ret; + if (xfer->tx_buf || + (master->flags & SPI_MASTER_MUST_TX_SG)) { + ret = spi_map_buf(master, tx_dev, &xfer->tx_sg, + (void *)xfer->tx_buf, xfer->len, + DMA_TO_DEVICE); + if (ret != 0) + return ret; + } + + if (xfer->rx_buf || + (master->flags & SPI_MASTER_MUST_RX_SG)) { + ret = spi_map_buf(master, rx_dev, &xfer->rx_sg, + xfer->rx_buf, xfer->len, + DMA_FROM_DEVICE); + if (ret != 0) { + spi_unmap_buf(master, tx_dev, &xfer->tx_sg, + DMA_TO_DEVICE); + return ret; + } } } diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 9ffa506..8b70419 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -357,6 +357,8 @@ struct spi_master { #define SPI_MASTER_NO_TX BIT(2) /* can't do buffer write */ #define SPI_MASTER_MUST_RX BIT(3) /* requires rx */ #define SPI_MASTER_MUST_TX BIT(4) /* requires tx */ +#define SPI_MASTER_MUST_RX_SG BIT(5) /* requires rx sg_list */ +#define SPI_MASTER_MUST_TX_SG BIT(6) /* requires tx sg_list */ /* lock and mutex for SPI bus locking */ spinlock_t bus_lock_spinlock; -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
